Stereospecificity of Corynebacterium glutamicum 2,3-butanediol dehydrogenase and implications for the stereochemical purity of bioproduced 2,3-butanediol
| Autor: | Bernhard J. Eikmanns, Dušica Radoš, David L. Turner, Eugenia Hoffart, Ana Rute Neves, Helena Santos, Bastian Blombach, Teresa Catarino |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Magnetic Resonance Spectroscopy Stereochemistry Carboxy-Lyases Dehydrogenase Applied Microbiology and Biotechnology Corynebacterium glutamicum Substrate Specificity 03 medical and health sciences chemistry.chemical_compound Stereospecificity 2 3-Butanediol Escherichia coli Butylene Glycols chemistry.chemical_classification biology Acetoin Lactococcus lactis Substrate (chemistry) General Medicine biology.organism_classification Recombinant Proteins Acetolactate Synthase Alcohol Oxidoreductases 030104 developmental biology Enzyme chemistry Biochemistry Metabolic Engineering Biotechnology |
| Zdroj: | Applied microbiology and biotechnology. 100(24) |
| ISSN: | 1432-0614 |
| Popis: | The stereochemistry of 2,3-butanediol (2,3-BD) synthesis in microbial fermentations is important for many applications. In this work, we showed that Corynebacterium glutamicum endowed with the Lactococcus lactis genes encoding α-acetolactate synthase and decarboxylase activities produced meso-2,3-BD as the major end product, meaning that (R)-acetoin is a substrate for endogenous 2,3-butanediol dehydrogenase (BDH) activity. This is curious in view of the reported absolute stereospecificity of C. glutamicum BDH for (S)-acetoin (Takusagawa et al. Biosc Biotechnol Biochem 65:1876–1878, 2001). To resolve this discrepancy, the enzyme encoded by butACg was produced in Escherichia coli and purified, and the stereospecific properties of the pure protein were examined. Activity assays monitored online by 1H-NMR using racemic acetoin and an excess of NADH showed an initial, fast production of (2S,3S)-2,3-BD, followed by a slow (∼20-fold lower apparent rate) formation of meso-2,3-BD. Kinetic parameters for (S)-acetoin, (R)-acetoin, meso-2,3-BD and (2S,3S)-BD were determined by spectrophotometric assays. Vmax values for (S)-acetoin and (R)-acetoin were 119 ± 15 and 5.23 ± 0.06 μmol min−1 mg protein−1, and Km values were 0.23 ± 0.02 and 1.49 ± 0.07 mM, respectively. We conclude that C. glutamicum BDH is not absolutely specific for (S)-acetoin, though this is the preferred substrate. Importantly, the low activity of BDH with (R)-acetoin was sufficient to support high yields of meso-2,3-BD in the engineered strain C. glutamicum ΔaceEΔpqoΔldhA(pEKEx2-als,aldB,butACg). Additionally, we found that the BDH activity was nearly abolished upon inactivation of butACg (from 0.30 ± 0.03 to 0.004 ± 0.001 μmol min−1 mg protein−1), indicating that C. glutamicum expresses a single BDH under the experimental conditions examined. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|